Numerical study on roll dynamics of damaged ship in beam waves and calm water

Abstract

Computational fluid dynamics is used to study the roll dynamics of a damaged ship in beam waves with various steepnesses and in calm water. The wave-making method, which combines the velocity-inlet boundary and momentum source with the fifth-order Stokes theory, is employed for wave generation. The SST k-ω turbulence model with a modification to the turbulent viscosity in Reynolds stress is adopted to prevent the over-production of turbulence in the numerical wave tank. The lateral drift restrained model with a combined dynamic mesh strategy is utilized to deal with the coupled heave-sway-roll motions of the ship. First, benchmarking tests are performed, including wave generation and roll response of the damaged ship in regular beam waves. Then, the effects of incident wave steepness on the roll response of the damaged ship are analyzed. For different wave steepnesses, the ship roll motion is dominated by the first-order harmonic component. The second-order component increases with the increase of wave steepness. Finally, the roll hydrodynamic coefficients for different parts of the damaged ship are investigated with different rolling parameters. The added moment of inertia for the whole damaged ship is mainly attributed to the external hull composition and changes slightly with the change of roll amplitude and frequency. The added moment of inertia for the compartments could be negative in particular cases. The damping coefficients of the whole damaged ship and external hull increase with the increase of roll amplitude and frequency, while that of the compartments appears complicated with the change of roll amplitude and frequency.